This invention relates to a fluted plasticboard and more particularly to the method and apparatus for sealing of the open edge wall of a fluted plasticboard in which a corrugated core separates the opposed planar face members. Fluted board members formed of plastic have been developed and can be used in various applications in place of corrugated cardboard as well as in other applications which require a moisture resistant board or the other properties of plastic. A serpentine corrugated core member is located between spaced plastic sheet-like boards and are bonded along the crown or other edge portions of the serpentine core. Extruded fluted plasticboard is also manufactured in which the cross section defines planar surfaces separated by vertical spacing members defining square flutes and corresponding openings.
Such plasticboard is often used, for example, not only in containers but in display boards and the like. The United States Post Office has indicated that a container formed of a fluted plasticboard has a life of about nine times that of a conventional corrugated paper board. Although the plasticboard may have a significantly greater material cost factor, the savings and long life are such that significant increased usage of such material is occurring and even greater usage is anticipated.
The plasticboard is conveniently formed in large sheets with the board openings at the exposed edge walls of the core. These openings permit the entry of dirt and other foreign matter. The sealing of such edge walls is highly desirable.
Various methods have been suggested for the sealing of edge walls in laminated boards which might be applied to a fluted board. For example, U.S. Pat. No. 4,238,263 which issued Dec. 9, 1980 discloses the method of edge sealing a plastic laminate by passing an exposed edge wall between a pair of angularly related rollers which are located to engage the opposite corners or edges of the edge wall. A heating unit is applied to heat the edges of the laminated member just prior to passing between the rollers, which then serve to deform and move the edges downwardly into overlapped relationship to seal the edge. U.S. Pat. No. 4,201,609 which issued May 6, 1980 discloses a method of joining the face sheets of a laminate member wherein projecting edge portions are heated by a blast of hot air to soften the outer layers and deflect the softened edge portions toward each other substantially in the central plane of the material and melt to form a sealed end wall.
U.S. Pat. No. 3,711,352 which issued Jan. 16, 1973 discloses a paperboard with a fluted core in which the exposed edge walls of the fluted core is removed from adjacent the face sheets to provide projecting sheet portions which are folded upon themselves in a suitable automated apparatus and sealed to each other to seal the open edge.
Although such systems have been proposed, they all have certain disadvantages because of the complexity of the system or the special treatment required of the fluted board such as the removal of the fluted portion to provide the edges to effectively move into overlapping engagement.
Although various systems have been suggested for sealing of the edge, makers and users of fluted plasticboard have generally recognized that a practical high speed and effective sealing method and apparatus which produces an end product with a smooth and acceptable sealed edge is not readily available.
There is therefore a need for a simple, preferably on-line system, to process fluted plasticboard edges as manufactured and processed to seal the exposed edge in an aesthetically pleasing sealed edge structure.